摘要
为探讨湖北省建始县土壤硒分布特征、硒的有效性及影响因素,本研究基于2015-2020年建始县土地质量地球化学评价调查结果,以建始县全域土壤及典型剖面为研究对象,分析不同土壤类型硒含量特征、土壤垂直剖面硒含量分布、土壤硒与理化性质的相关性。建始县土壤硒含量介于0.08~64.20 mg/kg,平均值为0.94 mg/kg,总体上属于足硒及富硒范畴。在建始县主要的土壤类型中,红壤、棕壤、黄壤中硒含量较高,紫色土中硒含量较低。土壤中硒含量在垂向剖面上变化明显,随着土壤剖面深度的增加,土壤硒含量逐渐降低,与土壤有机质的变化趋势一致。土壤中SiO2、Al2O3、TFe2O3和CaO等含量与硒含量呈现显著正相关,土壤硒与铬、镉、镍、钼等元素相关性较强,存在伴生关系。同时土壤有效硒含量与土壤pH和阳离子交换量存在显著的正相关。结果表明,土壤中硒的来源与土壤有机质密切相关,土壤硒与重金属伴生问题是富硒土壤开发利用的重要限制条件,提高土壤pH是增强硒生物有效性的有效技术途径。
硒是人体必需的微量营养元素,其作为谷胱甘肽过氧化物酶系统的重要组成而参与人体抗氧化系统的运
全球土壤的硒含量均值为0.4 mg/kg,中国有51%国土面积土壤硒含量缺乏,其中有1/3的地带极度缺
土壤理化性质对土壤硒生物有效性具有重要影响。硒在土壤中受到“吸附-解吸”、“沉淀-溶解”和“氧化-还原”等过程的影
前人对恩施土壤硒资源的调查研究多集中于土壤硒的水平分布或仅关注高硒或硒中毒区域硒的赋存特征和健康风
研究区域为湖北省恩施土家族苗族自治州建始县,位于湖北西南武陵山腹地,亚热带季风湿润型山地气候,地理坐标为北纬30°06′~30°54′,东经109°32′~110°12′,生态优良,资源富集,素有“金建始”美誉。地处云贵高原的东延部分,县境地貌形态主要有岩溶地貌和构造地貌2种。土壤类型以黄棕壤、棕壤、黄壤为主。
根据DZ/T 0295-2016《土地质量地球化学评价规范》等相关要求,对建始县进行土壤硒资源详查。本研究数据包含《1∶25 万湖北省长阳-恩施多目标区域地球化学调查》《湖北省建始县土地质量地球化学评价(一期)》《建始县土地质量地球化学评价暨土壤硒资源普查(内部资料)》项目样本数据,本次调查以耕、园、草地及药材基地为主,其中表层土壤平均采样密度为17个/k
样品采集方法及精度按照DZ/T 0295-2016《土地质量地球化学评价规范》要求进行。
样品制备、样品分析等方法及质量要求参照中国地质调查局DZ/T 0285-2014 《多目标区域地球化学调查规范(1∶250000)》、DD 2005-03《生态地球化学评价样品分析技术要求》、DZ/T0295-2016《土地质量地球化学评价规范》等相关技术标准执行。土壤样品元素分析方法见
分析方法 Analysis method | 简称 Abbreviation | 测定元素或指标 Index |
---|---|---|
电感耦合等离子体原子发射光谱法 Inductively coupled plasma atomic emission spectrometry | ICP-OES | Mn、Ni、CaO、MgO |
电感耦合等离子体质谱法 Inductively coupled plasma mass spectrometry | ICP-MS | Co、Cd、Pb、Cu、Zn、Mo |
X射线荧光光谱法 X-ray fluorescence spectrometry | XRF |
SiO2、Al2O3、 TFe2O3、Cr、P、S |
原子荧光光谱法 Atomic fluorescence spectrometry | AFS | As、Hg、Se |
离子选择性电极法 Ion-selective electrode method | ISE | F |
容量法 Volumetric method | VOL |
有机碳 Organic carbon |
电极法(水土质量比 2.5∶1) Ion-selective electrode method (water/soil of 2.5∶1(w/w)) | ISE | pH |
参考谭见
如
土壤类型 Soil type | 样本数 Numbers | 硒含量/(mg/kg) Se contents | 最小值/(mg/kg) Minimum value | 最大值/(mg/kg) Maximum value | 标准差/(mg/kg) Standward deviation | 变异系数/% Variation coefficient |
---|---|---|---|---|---|---|
水稻土 Paddy soil | 577 | 0.90 | 0.08 | 13.54 | 1.44 | 160.3 |
潮土 Moisture soil | 60 | 0.72 | 0.21 | 1.53 | 0.36 | 49.9 |
黄棕壤 Yellow brown soil | 5 606 | 0.85 | 0.13 | 64.20 | 1.73 | 204.2 |
棕壤 Brown soil | 1 550 | 1.21 | 0.16 | 26.00 | 1.61 | 132.4 |
石灰土 Lime soil | 403 | 0.56 | 0.12 | 7.16 | 0.82 | 146.7 |
黄壤 Yellow soil | 2 056 | 1.14 | 0.08 | 38.43 | 2.33 | 205.0 |
红壤 Red soil | 48 | 2.11 | 0.15 | 12.60 | 3.10 | 147.0 |
紫色土 Purple soil | 284 | 0.34 | 0.08 | 2.78 | 0.26 | 76.4 |
草甸土 Meadaw soil | 94 | 1.09 | 0.30 | 19.90 | 2.02 | 185.2 |
全部样品 Total | 10 678 | 0.94 | 0.08 | 64.20 | 1.81 | 191.3 |
本研究中,根据剖面深度将土壤剖面分为0~20、20~70、70~120、120~150和150~200 cm,不同深度土壤的总硒和有机质含量差异较大,供试土壤剖面逐一对应不同深度的土壤硒含量分别为1.61、0.78、0.47、0.45、0.38 mg/kg。随着剖面深度的增加,土壤中的硒含量逐渐降低,可能是受到淋溶作用或生物累积作用导致土壤浅层富集(

图1 不同土壤剖面采样深度的土壤硒含量(A)和有机质含量(B)
Fig.1 Soil selenium(A) and organic matter(B) in different profile sampling depth
由
氧化物 Oxide | 平均值/% Average | 最小值/% Minimum | 最大值/% Maximum | 标准差/% Standard deviation | 变异系数/% Variation coefficient |
---|---|---|---|---|---|
SiO2 | 68.39 | 41.44 | 88.42 | 4.62 | 6.70 |
Al2O3 | 13.08 | 4.22 | 21.23 | 2.07 | 15.80 |
TFe2O3 | 5.68 | 0.79 | 19.26 | 1.16 | 20.40 |
MgO | 1.76 | 0.24 | 17.11 | 1.49 | 84.70 |
CaO | 0.59 | 0.07 | 18.02 | 0.93 | 156.90 |
项目 Item | SiO2 | Al2O3 | TFe2O3 | MgO | CaO |
---|---|---|---|---|---|
皮尔逊相关性 Pearson correlation |
0.15 |
0.20 |
0.04 | 0.003 |
0.08 |
显著性(双侧) Significance(Two-tailed) | 0.000 | 0.000 | 0.000 | 0.805 | 0.000 |
注: “***”表示极显著差异(P<0.001)。Note: *** indicates significant difference(P<0.001).

图2 土壤硒与其他元素之间的相关性
Fig.2 Correlation between soil selenium and other elements
“*”代表差异极显著(P<0.01)。 * indicates the significant difference (P<0.01).
土壤pH是影响土壤硒有效性的重要因素,能够影响硒的形态和有效性,如

图3 土壤有效硒与土壤pH(A)、阳离子交换量(B)以及土壤有机碳(C)的关系
Fig.3 The relationship between soil available selenium and soil pH(A), cation exchange capacity(B) and soil organic carbon(C)
“r”值代表Pearson相关系数。“r” values mean Pearson’s correlation coefficients.
土壤有效硒含量与土壤阳离子交换量也存在显著的正相关关系,相关系数为0.40(n=147,P<0.01)(
在调查区的土壤中,红壤硒含量(2.11 mg/kg)显著高于其他土壤类型,依次为棕壤(1.21 mg/kg)>黄壤(1.14 mg/kg)>草甸土(1.09 mg/kg)>水稻土(0.90 mg/kg)>黄棕壤(0.85 mg/kg)、潮土(0.72 mg/kg)>石灰土(0.56 mg/kg)>紫色土(0.34 mg/kg)。紫色土主要发育于三叠系巴东组紫红色粉砂质页岩,其抗蚀力弱,物理风化作用强烈,常处于幼年发育阶段,导致硒含量低于其他类型土壤。红壤和黄壤成土母质多为石灰岩和泥质页岩等,其质地黏重且盐基饱和度低,因此有利于硒的富集,故而硒含量相对较高。此外,棕壤主要分布于海拔800~1 500 m以上地区,气温较低,土壤有机质分解速度较慢,从而有利于硒的积累。土壤金属氧化物含量主要取决于成土母质类型、风化和淋溶迁移作用等,不同土壤类型的金属氧化物组成差异巨大。在本研究中土壤SiO2、Al2O3、Fe2O3和CaO等含量与Se呈现显著正相关,同时覃建勋
此外,本研究中土壤有机质和硒含量随着土壤剖面深度的增加而逐渐降低,呈现相同的变化趋势,这从侧面证实了土壤有机质对土壤硒含量的潜在影响。Lü
本研究中土壤硒与镉、铬、汞和镍等重金属存在伴生关系。耿建梅
土壤有效硒含量与土壤pH和阳离子交换量呈现显著正相关性,因此,土壤有效硒含量可能受到土壤pH和阳离子交换量的调控。Lü
综上所述,建始县土壤硒含量均值显著高于中国土壤(A层)的硒含量均值,土壤硒资源极为丰富。受土壤母质和成土过程的影响,不同土壤类型硒含量表现为红壤>棕壤>黄壤>草甸土>水稻土>黄棕壤>潮土>石灰土。土壤中硒的来源与土壤有机质密切相关,土壤硒与重金属伴生问题是富硒土壤开发利用的重要限制条件,同时提高土壤pH是增强硒有效性的有效途径。本研究探究了建始县土壤硒分布特征以及土壤理化性质等对土壤有效硒的影响,下一步将针对硒与重金属伴生问题,基于土壤硒与重金属含量对耕地土壤进行详细的划分,同时对富硒土壤中硒的赋存形态进行更深入的研究,以期为土壤硒资源的安全利用提供依据。
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